共查询到20条相似文献，搜索用时 31 毫秒
1.
Robb Eric S. Moss Joseph A. Caliendo Loren R. Anderson 《Soil Dynamics and Earthquake Engineering》1998,17(7-8):519-523
In certain regions of the world, designing deep foundations to withstand seismic loading is a reality. Seismic loading of structures and foundations reaches its most critical state as a cyclic lateral force. The response of soils and foundations to repetitive lateral forces is highly complex, relegating most design methods to be based upon overly conservative rules-of-thumb. The primary objective of this research was to analyze the mechanics of seismic loading on pile groups in clay soils. To achieve this a model testing facility was constructed to house a fully instrumented 1×5 model pile group that was subjected to cyclic lateral loading. An empirically based method for pile group design is suggested based upon the results generated from model pile group testing. 相似文献
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Zhi-Fan Xia Guan-Lin Ye Jian-Hua Wang Bin Ye Feng Zhang 《Soil Dynamics and Earthquake Engineering》2010
It is known that a series of aftershocks might follow a mainshock, which may cause further damages on civil engineering structures. So it is necessary to investigate the dynamic response of structures undergone several shocks. This study presents a numerical analysis of repeated shake-consolidation process for an earth embankment founded on liquefiable foundation soils. Analysis is carried out using an effective stress-based, fully coupled, finite element method. The behaviors of the foundation soils are described by means of a cyclic mobility constitutive model which was developed at the bases of modified Cam-clay model by introducing concepts such as stress-induced anisotropy, over-consolidation, and structure. Results show that the cyclic mobility constitutive model can reflect the dynamic response of liquefiable soils. Special emphasis is given to analyze the result of excess pore water pressures, stress path, acceleration, and deformations during the two seismic excitation and consolidation process. 相似文献
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Advanced frame element for seismic analysis of masonry structures: model formulation and validation 
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下载免费PDF全文 This paper presents a masonry panel model for the nonlinear static and dynamic analysis of masonry buildings suitable for the seismic assessment of new and existing structures. The model is based on an equivalent frame idealization of the structure and stems from previous research on force‐based frame elements. The element formulation considers axial, bending, and shear deformations within the framework of the Timoshenko beam theory. A phenomenological cyclic section law that accounts for the shear panel response is coupled, through equilibrium between shear and bending forces along the element, with a fiber‐section model that accounts for the axial and bending responses. The proposed panel model traces with a low computational burden and numerical stability the main aspects of the structural behavior of masonry panels and is suitable for analyses of multi‐floor buildings with a relatively regular distribution of openings and with walls and floors organized to grant a box‐like behavior under seismic loads. The model capabilities are validated though analyses of simple unreinforced masonry panels and comparisons with published experimental results. The model accuracy is strongly dependent on the fiber and shear constitutive laws used. However, the formulation is general, and laws different from those employed in this study are easily introduced without affecting the model formulation. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Under seismic excitation, liquefied clean medium to dense cohesionless soils may regain a high level of shear resistance at large shear strain excursions. This pattern of response, known as a form of cyclic mobility, has been documented by a large body of laboratory sample tests and centrifuge experiments. A plasticity-based constitutive model is developed with emphasis on simulating the cyclic mobility response mechanism and associated pattern of shear strain accumulation. This constitutive model is incorporated into a two-phase (solid–fluid), fully coupled finite element code. Calibration of the constitutive model is described, based on a unique set of laboratory triaxial tests (monotonic and cyclic) and dynamic centrifuge experiments. In this experimental series, Nevada sand at a relative density of about 40% is employed. The calibration effort focused on reproducing the salient characteristics of dynamic site response as dictated by the cyclic mobility mechanism. Finally, using the calibrated model, a numerical simulation is conducted to highlight the effect of excitation frequency content on post-liquefaction ground deformations. 相似文献
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The paper presents a hysteretic damage model for the response simulation of structural components with strength and stiffness deterioration under cyclic loading. The model is based on 1D continuum damage mechanics and relates any 2 work‐conjugate response variables such as force‐displacement, moment‐rotation, or stress‐strain. The strength and stiffness deterioration is described by a continuous damage variable. The formulation uses a criterion based on the hysteretic energy and the maximum or minimum deformation for damage initiation with a cumulative probability distribution function for the damage evolution. A series of structural component response simulations showcase the ability of the model to describe different types of hysteretic behavior. The relation of the model's damage variable to the Park‐Ang damage index is also discussed. Because of its consistent and numerically robust formulation, the model is suitable for the large‐scale seismic response simulation of structural systems with strength and stiffness deterioration. 相似文献
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Reinforced concrete shear walls are used because they provide high lateral stiffness and resistance to extreme seismic loads. However, with the increase in building height, these walls have become slenderer and hence responsible of carrying larger axial and shear loads. Because 2D/3D finite element inelastic models for walls are still complex and computationally demanding, simplified but accurate and efficient fiber element models are necessary to quickly assess the expected seismic performance of these buildings. A classic fiber element model is modified herein to produce objective results under particular loading conditions of the walls, that is, high axial loads, low axial loads, and nearly constant bending moment. To make it more widely applicable, a shear model based on the modified compression field theory was added to this fiber element. Consequently, this paper shows the formulation of the proposed element and its validation with different experimental results of cyclic tests reported in the literature. It was found that in order to get objective responses in the element, the regularization techniques based on fracture energy had to be modified, and nonlinearities because of buckling and fracture of steel bars, concrete crushing, and strain penetration effects were needed to replicate the experimental cyclic behavior. Thus, even under the assumption of plane sections, which makes the element simple and computationally efficient, the proposed element was able to reproduce the experimental data, and therefore, it can be used to estimate the seismic performance of walls in reinforced concrete buildings. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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A macroscopic model that consists of distributed hysteretic springs and frequency dependent -pots is utilized to model the lateral soil reaction and a practical method based on one-dimensional finite element formulation is developed to compute the nonlinear response of single piles under dynamic lateral loads. The model is physically motivated, adequate for cohesive and cohesionless soils, and involves standard geotechnical parameters. Only two parameters have to be calibrated by fitting experimental data. Hysteretic and radiation damping are modeled realistically within the practical range of amplitudes and frequencies. The model is calibrated and validated against five well instrumented full-scale experiments and typical values for the range of the model-parameters are provided. Subsequently, the developed model is utilized to study the nonlinear seismic response of single piles. Finally, the developed method and the calibrated model are used to predict the inertial and seismic response of one of the piles used in the foundation of the Ohba bridge near Tokyo, Japan. 相似文献
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A study on the seismic response of massive flexible strip-foundations embedded in layered soils and subjected to seismic excitation is presented. Emphasis is placed on the investigation of the system response with the aid of a boundary element–finite element formulation proper for the treatment of such soil–structure interaction problems. In the formulation, the boundary element method (BEM) is employed to overcome the difficulties that arise from modeling the infinite soil domain, and the finite element method (FEM) is applied to model the embedded massive flexible strip-foundation. The numerical solution for the soil–foundation system is obtained by coupling the FEM with the BEM through compatibility and equilibrium conditions at the soil–foundation and soil layer interfaces. A parametric study is conducted to investigate the effects of foundation stiffness and embedment on the seismic response. 相似文献
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Accurate prediction of the liquefaction of saturated soils is based on strong coupling between the pore fluid phase and soil skeleton. A practical numerical method for large strain dynamic analysis of saturated soils is presented. The u–p formulation is used for the governing equations that describe the coupled problem in terms of soil skeleton displacement and excess pore pressure. A mixed finite element and finite difference scheme related to large strain analysis of saturated soils based on the updated Lagrangian method is given. The equilibrium equation of fluid-saturated soils is spatially discretized by the finite element method, whereas terms associated with excess pore pressure in the continuity equation are spatially discretized by the finite difference method. An effective cyclic elasto-plastic constitutive model is adopted to simulate the non-linear behavior of saturated soils under dynamic loading. Several numerical examples that include a saturated soil column and caisson-type quay wall are presented to verify the accuracy of the method and its usefulness and applicability to solutions of large strain liquefaction analysis of saturated soils in practical problems. 相似文献
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An equivalent linear algorithm with frequency- and pressure-dependent moduli and damping for the seismic analysis of deep sites 总被引：4，自引：0，他引：4
The seismic analysis of soil deposits is most often carried out with an iterative computational scheme, proposed by Seed and Idriss, in which inelastic effects are only approximately modeled through soil degradation curves. Laboratory experimental data indicate that for highly confined materials, the standardized reduction curves commonly used overestimate the capacity of soils to dissipate energy. This paper first presents the results obtained with a simple four-parameter constitutive soil model, which when used to simulate cyclic loading, produces results that agree well with available laboratory experiments for soils under arbitrarily large confining pressures. Thereafter, a frequency- and pressure-dependent iterative algorithm for seismic amplification is proposed, which provides time histories that match well the results obtained with a true non-linear model. Finally, the modified linear iterative analysis is successfully used for the seismic analysis of a 1 km deep model for the Mississippi embayment near Memphis, Tennessee, and a class-A prediction of the seismic amplification in Treasure Island during the Loma Prieta earthquake. 相似文献
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V. N. Kutergin V. V. Sevost’yanov K. V. Pankov R. G. Kal’bergenov L. V. Grigor’eva 《Water Resources》2017,44(7):968-977
A method is proposed for assessing the seismic resistance of soils, involving the analysis of seismic data (with soil conditions taken into account), the choice and specification of amplitude–frequency spectrum parameters, experimental studies of soil samples with specified cyclic load parameters, analysis of the dependence of soil behavior on the overload factor, and calculating the ultimate overload factor based on the comparison of accepted and ultimate effect levels. The paper gives the results of practical application of the developed approach to assessing the seismic resistance of a shelf area in the Northern Caspian Sea. 相似文献
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Y. H. Chai 《地震工程与结构动力学》2005,34(1):83-96
Seismic performance of structures is related to the damage inflicted on the structure by the earthquake, which means that formulation of performance‐based design is inherently coupled with damage assessment of the structure. Although the potential for cumulative damage during a long‐duration earthquake is generally recognized, most design codes do not explicitly take into account the damage potential of such events. In this paper, the classical low‐cycle fatigue model commonly used for seismic damage assessment is cast in a framework suitable for incorporating cumulative damage into seismic design. The model, in conjunction with a seismic input energy spectrum, may be used to establish an energy‐based seismic design. In order to ensure satisfactory performance in a structure, the cyclic plastic strain energy capacity of the structure is designed to be larger than or equal to the portion of seismic input energy contributing to cumulative damage. The resulting design spectrum, which depends on the duration of the ground motion, indicates that the lateral strength of the structure must be increased in order to compensate for the increased damage due to an increased number of inelastic cycles that occur in a long‐duration ground motion. Examples of duration‐dependent inelastic design spectra are developed using parameters currently available for the low‐cycle fatigue model. The resulting spectra are also compared with spectra developed using a different cumulative damage model. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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《地震研究进展（英文）》2022,2(4):100170
Soils with spatial variability are the product of natural history. The mechanical properties tested by soil samples from boreholes in the same soil layer may be different. Underground structure service in surrounding soils, their seismic response is controlled by the deformation of the surrounding soils. The variability of soil mechanical parameters was not considered in the current research on the seismic response of underground structures. Therefore, a random field model was established to describe the spatial variability of surrounding soils based on the random field theory. Then the seismic response of underground structures in the random field was simulated based on the time-domain explicit global FEM analysis, and the soil mechanical parameters and earthquake intensity influencing the seismic response of surrounding soils and underground structures were studied. Numerical results presented that, the randomness of soil parameters does not change the plastic deformation mode of surrounding soils significantly. The variation coefficients of inter-story deformation of structures and lateral deformation of columns are much smaller than that of mechanical parameters, and the randomness of soil parameters has no obvious effect on the structural deformation response. 相似文献
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An automatically adaptive element free method is presented to analyze the seismic response of liquefiable soils.The method is based on the element free Galerkin method (EFGM) and the fission procedure that is part of h-refinement,indicated by error estimation. In the proposed method, a posteriori error estimate procedure that depends on the energy normof stress and the T-Belytschko (TB) stress recovery scheme is incorporated. The effective cyclic elasto-plastic constitutivemodel is used to describe the nonlinear behavior of the saturated soil. The governing equations are established by u-pformulation. The proposed method can effectively avoid the volumetric locking due to large deformation that usually occursin numerical computations using the finite element method (FEM). The efficiency of the proposed method is demonstratedby evaluating the seismic response of an embankment and comparing it to results obtained through FEM. It is shown that theproposed method provides an accurate seismic analysis of saturated soil that includes the effects of liquefaction 相似文献
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The aim of this work is to model beam‐column behavior in a computationally effective manner, revealing reliably the overall response of reinforced concrete members subjected to intensive seismic loading. In this respect, plasticity and damage are considered in the predominant longitudinal direction, allowing for fiber finite element modeling, while in addition the effect of inelastic buckling of longitudinal rebars, which becomes essential at later stages of intensive cyclic loading, is incorporated. Α smooth plasticity‐damage model is developed for concrete, accounting for unilateral compressive and tensile behavior, nonlinear unloading and crack closure phenomena. This is used to address concrete core crushing and spalling, which triggers the inelastic buckling of longitudinal rebars. For this reason, a uniaxial local stress‐strain constitutive relation for steel rebars is developed, which is based on a combined nonlinear kinematic and isotropic hardening law. The proposed constitutive model is validated on the basis of existing experimental data and the formulation of the buckling model for a single rebar is developed. The cross section of rebar is discretized into fibers, each one following the derived stress‐strain uniaxial law. The buckling curve is determined analytically, while equilibrium is imposed at the deformed configuration. The proposed models for concrete and rebars are embedded into a properly adjusted fiber beam‐column element of reinforced concrete members and the proposed formulation is verified with existing experimental data under intensive cyclic loading. 相似文献
18.
Constitutive equations for drained cohesionless soils under triaxial stress states, based on a microslip model with internal friction, are proposed and applied to the analysis of the seismic response of soil deposits. The microslips, assumed localized in the discontinuity surfaces passing through the particle-to-particle contacts, describe the effects of the sliding and rolling between grains of sand. Once the response of the model under cyclic shearing stresses and strains superimposed on the geostatic stress state has been analysed, the constitutive equations are applied to a one-dimensional shear model for the dynamic analysis of the layered deposits. An application to an instrumented soil deposit is then developed, the experimental results of which refer to both strong and weak motion earthquakes; the comparisons between the experimental and theoretical results point out the peculiarities and validity limits of the model. The model here developed may be applied also to the analysis of two- and three-dimensional sites. 相似文献
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Suitable materials for use as shell of embankment dams are clean coarse-grained soils or natural rockfill. In some sites these materials may not be available at an economic distance from the dam axis. The use of in-situ cohesive soils reinforced with geotextiles as the shell is suggested in this study for such cases. Dynamic behavior of reinforced embankment dam is evaluated through fully coupled nonlinear effective stress dynamic analysis. A practical pore generation model has been employed to incorporate pore pressure build up during cyclic loading. Parametric analyses have been performed to study the effect of reinforcements on the seismic behavior of the reinforced dam. Results showed that reinforcements placed within the embankment reduce horizontal and vertical displacements of the dam as well as crest settlements. Maximum shear strains within the embankment also decreased as a result of reinforcing. Furthermore, it was observed that reinforcements cause amplification in maximum horizontal crest acceleration. 相似文献
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The seismic response characteristics of underground structures in saturated soils are investigated. A fully fluid-solid coupling dynamic model is developed and implemented into ABAQUS with a user-defined element to simulate the dynamic behavior of saturated soils. The accuracy of the model is validated using a classic example in literature. The performance of the model is verified by its application on simulating the seismic response characteristics of a subway station built in saturated soils. The merits of the model are demonstrated by comparing the difference of the seismic response of an underground structure in saturated soils between using the fully coupling model and a single-phase medium model. The study finds that the fully coupling model developed herein can simulate the dynamic response characteristics of the underground structures in saturated soils with high accuracy. The seismic response of the underground structure tends to be underestimated by using the single-phase medium model compared with using the fully coupling model, which provides a weaker confining action to the underground structure. 相似文献